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<html lang="cn">
<head>
    <meta charset="UTF-8">
    <title>结构伪类</title>
    <style type="text/css">
        table {
            border-collapse: collapse;
        }

        tr {
            height: 30px;
        }

        td {
            width: 100px;
            border: 2px solid black;
            text-align: center;
        }
        tr:nth-child(1)>td::after{
            content: "表头";
            font-weight: bold;
        }
        tr:first-child~tr>td::after{
            content: "单元格";
        }
        tr:nth-child(even){
            background-color: aqua;
        }
    </style>
</head>
<body>
<table>
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</table>
</body>
</html>